Organophilic compositions

ABSTRACT

There is disclosed a organophilic composition which comprises a mixture of a smectite clay and a particulate second inorganic material, the mixture having been treated with a quaternary ammonium compound which is capable of rendering the smectite clay organophilic and the second inorganic material constituting at least 10% by weight of the mixture of smectite clay, second inorganic material and quaternary ammonium compound. 
     The organophilic composition is useful for gelling organic solvents and compositions containing organic solvents.

This is a division, of application Ser. No. 940,988, filed Dec. 12, 1986 now U.S. Pat. No. 4,743,306.

This invention relates to organophilic compositions and more particularly but not exclusively is concerned with organophilic compositions suitable for improving the thixotropic properties of cross-linkable unsaturated polyester resin compositions and for gelling organic solvents and compositions containing significant amounts of organic solvents. The present invention is also concerned with a process for preparing organophilic compositions.

BACKGROUND OF THE INVENTION

Unsaturated polyester resin compositions containing gelling agents, or gellants, are well-known. For example, in the preparation of glass fibre laminates using unsaturated polyester resins as the bonding agent, it is known to use thixotropic gelling agents which permit easy mixing and spraying of the resins at high shear rates but which greatly increase the viscosity of the resins at low shear rates thus inhibiting the drainage of the resins on vertical surfaces. One of the most effective gelling agents for unsaturated polyester resins is a silica aerogel which is typically added to a solution of the resin in an unsaturated aromatic monomer, such as styrene, at a level of about 1% by weight, based on the weight of the solution. However, silica aerogels are extremely fine and very expensive and, because of their low bulk density, present storage and handling problems and constitute a health hazard.

Various attempts have been made to use organoclays as gelling agents for unsaturated polyester resins, which organoclays are generally smectite clays, e.g. montmorillonite, bentonite, hectorite or the like, at least part of the exchangeable cations of which are replaced by quaternary ammonium cations containing at least one alkyl group having from 10 to 24 carbon atoms.

SUMMARY OF THE INVENTION

According to one aspect of the present invention, there is provided an organophilic composition which comprises a mixture of a smectite clay and a particulate second inorganic material, the mixture having been treated with a quarternary ammonium compound which is capable of rendering the smectite clay organophilic and the second inorganic material constituting at least 5% by weight of the mixture of smectite clay, second inorganic material and quarternary ammonium compound.

The smectite clay may be, for example, bentonite, montmorillonite, hectorite, saponite or fullers earth.

The second inorganic material may be, for example, finely divided silica having an average particle diameter in the range from 0.005 μm to 0.5 μm. Preferably, the second inorganic material constitutes from 10% to 50% by weight of the mixture of smectite clay, second inorganic material and quarternary ammonium compound.

Advantageously, the quarternary ammonium compound has at least one alkyl radical having from 10 to 24 carbon atoms and most preferably is one which can be represented by the general formula: ##STR1## wherein R₁ is a saturated or unsaturated alkyl group having from 10 to 24 carbon atoms, R₂ and R₃ which may be the same or different, are each a saturated or unsaturated alkly group having from 1 to 24 carbon atoms or an aralkyl group having from 7 to 10 carbon atoms, R₄ is an alkyl group having from 1 to 6 carbon atoms or an aralkyl group having from 7 to 10 carbon atoms, and X is OH, Cl, Br, I, NO₂, CH₃ SO₄ or CH₃.COO. Examples of such quaternary ammonium compounds are the methyl benzyl dialkyl ammonium chlorides, the dimethyl dialkyl ammonium chlorides, the dimethyl benzyl alkyl ammonium chlorides, the benzyl trialkyl ammonium chlorides and the methyl trialkyl ammonium chlorides in which the alkyl group is a mixture of hydrocarbon radicals derived from tallow having from 14 to 20 carbon atoms but in which C₁₈ radicals predominate. (A typical analysis of such a mixture of hydrocarbon radicals contained in tallow is: C₁₄ 4.5%; C₁₅ 0.5%; C₁₆ 30.5%; C₁₇ 1.5%; C₁₈ 62% and C₂₀ 1.0%.) The hydrocarbon radicals may be partially unsaturated as in natural tallow or may be substantially completely saturated as a result of treating the tallow with hydrogen in the presence of a suitable catalyst.

Most preferably, the mixture of smectite clay and second inorganic material is treated with a mixture of dimethyl di-(hydrogenated tallow) ammonium chloride (2M2HT) and dimethyl benzyl hydrogenated tallow ammonium chloride (2MBHT) in proportions ranging from 25 mol % of 2MBHT and 75 mol % of 2M2HT to 100 mol % of 2MBHT and 0 mol % of 2M2HT.

It is also preferred to treat the mixture of smectite clay and second inorganic material with a quantity of quaternary ammonium compound or mixture of quaternary ammonium compounds such as to provide from 95 to 140 milliequivalents of quaternary ammonium compound(s) per 100 g of dry smectite clay.

According to another aspect of the present invention there is provided a process for preparing an organophilic composition, which process comprises preparing an aqueous suspension comprising a mixture of a smectite clay and a particulate second inorganic material, mixing with this aqueous suspension a quaternary ammonium compound capable of rendering the smectite clay organophilic, either in the molten state or in the form of an emulsion in water, and subjecting the resultant mixture to high shear mixing for a time sufficient to dissipate in the mixture at least 100KJ of energy per Kg of dry solids in the mixture, the second inorganic material being used in an amount sufficient to provide at least 5% by weight of the final mixture of smectite clay, second inorganic material and quaternary ammonium compound.

In the process of the present invention, the high shear mixing is preferably effected by passing the suspension through a homogeniser of the type in which the suspension is forced in the form of a thin film edgewise through a thin, hard surfaced gap under a pressure of at least 250 pounds per square inch (1.7 MPa) and at a high velocity. A suitable homogeniser is described in British Patent Specification No. 987176 (or in U.S. Pat. Nos. 3,039,703 and 3,162,379). Such a homogeniser is manufactured by the Matnon-Gaulin Company. Advantageously, the homogeniser is operated at a pressure of at least 1500 pounds per square inch (10.5 MPa). The amount of energy, in KJ per Kg of dry solids, dissipated in the mixture is given by the expression: ##EQU1## where P is the pressure in MPa exerted in the Manton--Gaulin homogeniser, n is the number of passes through the Manton-Gaulin homogeniser, and w is the weight in grams of dry solids in 1 liter of the aqueous mixture.

The mixture of smectite clay and second inorganic material after reaction with the quaternary ammonium compound(s) is preferably dewatered by filtration or by centrifugation, washed with water and thermally dried under conditions such that the temperature does not exceed 100° C. for more than a few minutes. The dry material may then be pulverised to facilitate its incorporation into, for example, a cross-linkable unsaturated polyester resin composition. Alternatively, the mixture of smectite clay and second inorganic material after reaction with the quarternary ammonium compound(s) may be partially dewatered for, example, by decantation and the thickened suspension thus formed spray dried to give dry material in the form of microspheres which may not require any pulverisation.

The organophilic composition of the invention is also suitable for gelling organic solvents such as toluene and xylene and compositions containing such solvents, and for thickening polar paint compositions such as "two-pack epoxy paints". Polar paint compositions are generally paints which contain organic solvents of medium to high polarity, such as ketones, esters, gylcol ether esters and alcohols. It is important that the organoclay thickener should disperse quickly and easily into the paint composition with the consumption of the minimum amount of energy. This is readily achieved using the organophilic composition of the present invention.

EMBODIMENTS OF THE INVENTION

The invention is illustrated by the following Examples.

EXAMPLE 1

An aqueous suspension of bentonite was prepared by mixing raw Wyoming sodium bentonite in a blunger with sufficient water to form a suspension containing 10% by weight of dry clay and with 1% by weight, based on the weight of dry clay, of tetrasodium pyrophosphate as a dispersing agent. The deflocculated suspension thus formed was passed through a No. 300 mesh British Standard sieve (nominal aperture 0.053 mm) and the undersize fraction was diluted to about 6% by weight of solids with water and subjected to a particle size separation in a nozzle discharge, disc centrifuge at a flow rate of 2 liters per minute. The fine fraction was then passed once through a Manton-Gaulin homogeniser at a pressure of 4000 psi (27.6 MPa). The energy dissipated in the suspension during the single pass through the Manton-Gaulin homogeniser was 673 KJ per Kg of dry clay.

Three aqueous suspension A, B and C were prepared each containing 6% by weight of a precipitated silica having a median ultimate particle diameter of 0.03μm. All three suspensions were formed initially by mixing the silica with the water by means of a laboratory stirrer.

Suspension A was then further treated by being passed once through the Manton-Gaulin homogeniser at a pressure of 4000 psi (27.6 MPa), the energy dissipated in the suspension being 443 KJ per Kg of dry silica.

Suspension B was further treated by means of a Silverson shrouded impeller mixer set to provide maximum shear for a time of 15 minutes. The energy dissipated in the suspension under these conditions is very difficult to estimate but it is believed to be of the order of 100 KJ per Kg.

Suspension C was given no further mechanical treatment.

The bentonite suspension was mixed with a suspension of silica in proportions such that the mixture contained 25% by weight of dry silica in the final dry organoclay/silica product and 48.9% by weight of dry clay. The remaining 26.1% is accounted for by the dry weight of the mixture of quaternary ammonium compounds. An aqueous suspension of a mixture consisting of 50 mol % of dimethyl di(hydrogenated tallow) ammonium chloride (2M2HT) and 50 mol % of dimethyl benzyl (hydrogenated tallow) ammonium chloride (2MBHT) was prepared by melting the quaternary ammonium compounds in the form in which they are available in commerce (75% by weight of the quaternary ammonium compound and 25% by weight of a mixture of isopropyl alcohol and water) and pouring them into hot water in proportions such as to form a 1.5% by weight emulsion of the mixed quaternary ammonium compounds in water.

Mixtures of bentonite suspension, silica suspension and quaternary ammonium compounds were prepared by the following methods:

1. The bentonite and silica suspensions were mixed together in the desired porportions using the Silverson mixer at the maximum shear setting for 15 minutes, during which time sufficient of the emulsion of mixed quaternary ammonium compounds was added to provide 105 milliequivalents of quaternary ammonium compounds 100 g of dry bentonite.

2. The bentonite and silica suspensions were mixed together using the Manton-Gaulin homogeniser for one pass at 4000 psi (27.5 MPa) and the emulsion of mixed quaternary ammonium compounds was added to the feed container of the Manton-Gaulin homogeniser in the same proportions as in method 1. The energy dissipated in the suspension was 1365 KJ per Kg of total dry solids.

3. The bentonite and silica suspensions were mixed together using the laboratory stirrer and the emulsion of mixed quaternary ammonium compounds was added as the stirring proceeded in the same proportions as in method 1.

4. The bentonite suspension and the emulsion of mixed quaternary ammonium compounds were mixed together using the Manton-Gaulin homogeniser for one pass at 4000 psi (27.6 MPa) and the suspension of silica was added to the feed container of the Manton-Gaulin homogeniser. The energy dissipated in the suspension was 1024 KJ per Kg of total dry solids.

A further mixture was prepared, as a control, by mixing together the bentonite suspension only and sufficient of the emulsion of mixed quaternary ammonium compounds in proportions such as to provide 105 milliequivalents of quaternary ammonium compounds per 100 g of dry bentonite using the Manton-Gaulin homogeniser for one pass at 4000 psi (27.6 MPa). The energy dissipated in the suspension was 1402 KJ per Kg of total dry solids.

In each case the organoclay suspension was filtered on a Buchner funnel, washed with hot water and dried for 16 hours at 60° C. in an air-swept oven. The dry product was then milled to pass through a seive of nominal aperture 0.080 mm.

1% by weight of each dry organoclay composition was incorporated into an unsaturated polyester resin composition using a laboratory stirrer rotating at 3,500 rpm. The resin was a rapid-curing, general--purpose polyester resin marketed by the Scott Bader Company Limited under the trade name "CRYSTIC 196". ("CRYSTIC" is a Registered Trade Mark), and, is believed to be a co-polymer of o-phthalic acid, fumaric acid and propylene glycol, having a number average molecular weight of about 3000.

The viscosity of the polyester resin composition containing the organoclay as a gelling agent was measured using a Brookfield Viscometer at a spindle speed of 0.5 rpm.

The results obtained are set forth in Table I.

                  TABLE I                                                          ______________________________________                                         Silica   Mixing       Viscosity                                                                               Thixotropy                                      suspension                                                                              Method       (mPa.s)  Index                                           ______________________________________                                         No silica                                                                               Manton-      1300     2.30                                                     Gaulin                                                                C        3             600     1.80                                            B        1            2800     2.78                                            A        2            3200     2.78                                            A        3             800     2.00                                            A        4            1280     2.30                                            ______________________________________                                    

These results show that in order to achieve a good gelling effect in the polyester resin, the silica suspension must be mixed with the bentonite suspension before the bentonite is contacted with the quaternary ammonium compounds, and that both the silica suspension and the bentonite/silica/quarternary ammonium compound mixture must be subjected to high shear mechanical working such that at least 100 KJ of energy per Kg of dry total solids is dissipated in the suspension.

The thixotropy index referred to in Table 1 is defined as the ratio of the viscosity of the composition as measured with a Brookfield Viscometer at 5 rpm to the viscosity measured with a Brookfield Viscometer at 50 rpm. The value of the thixotropy index should be as high as possible where shear thinning or pseudoplastic properties are sought.

EXAMPLE 2

The bentonite suspension and silica suspension "A" prepared as described in Example 1 above were mixed together in proportions such as to give 25% by weight of dry silica in the final dry organoclay/silica product and in the range of from 46.3% to 51.8% by weight of dry bentonite, depending upon the effective molecular weight of the mixture of quaternary ammonium compounds, and samples of the mixed suspension were passed once through the Manton-Gaulin homogeniser at 4000 psi (27.6 MPa). In each case there was added to the feed container of the Manton-Gaulin homogeniser sufficient of an emulsion containing 1% by weight of a mixture of 2M2HT and 2MBHT to provide 105 milliequivalents of mixed quaternary ammonium compounds per 100 g of dry bentonite, but the 2M2HT and the 2MBHT were mixed in different proportion in each case.

In each case the organoclay suspension was filtered, washed, dried and milled as described in Example 1 and 1% by weight of each dry organoclay was stirred into the same polyester resin composition as was described in Example 1. The viscosity of each polyester resin sample after the addition of the organoclay was measured by means of a Brookfield Viscometer at a spindle speed of 0.5 rpm and the results obtained are set forth in Table II.

                  TABLE II                                                         ______________________________________                                                   % by weight of                                                                           quarternary                                                mole % of   bento-  ammonium  Viscosity                                                                             Thixotropy                                2MBHT  2M2HT    nite    compounds                                                                              (mPa.s)                                                                               Index                                   ______________________________________                                          0     100      46.3    28.7    1200   1.90                                    25     75       47.5    27.5    1800   2.40                                    50     50       48.9    26.1    3200   2.78                                    75     25       50.3    24.7    3800   2.9                                     100     0       51.8    23.2    3600   2.8                                     ______________________________________                                    

EXAMPLE 3

The bentonite suspension and silica suspension "A" prepared as described in Example 1 above were mixed together in proportions such as to give 25% by weight of dry silica and 48.9% by weight of dry bentonite in the final dry organoclay/silica product, the remaining 26.1% being accounted for by the dry weight of the mixture of quaternary ammonium compound. Samples of the mixed suspension were passed once through the Manto-Gaulin homogeniser at 4000 psi (27.6 MPa). In each case there was added to the feed container of the

Manton-Gaulin homogeniser a quantity of an emulsion containing 1% by weight of a mixture consisting of 75 mol % of 2MBHT and 25 mol % of 2M2HT, the quantity being varied in each case in order to provide a different number of milliequivalents of mixed quaternary ammonium compounds per 100 g of dry bentonite.

In each case the organoclay suspension was filtered, washed, dried and milled as described in Example 1, and 1% by weight of each dry organoclay was stirred into the same polyester resin composition as was described in Example 1. The viscosity of each polyester resin after the addition of the organoclay was measured by means of a Brookfield Viscometer at spindle speed of 0.5 rpm and the results obtained are set forth in Table III.

                  TABLE III                                                        ______________________________________                                         Milli-equivalents                                                              of quarternary                                                                             % by weight of                                                     ammonium            quarternary                                                compounds per                                                                              bento-  ammonium  Viscosity                                                                             Thixotropy                                100 g of bentonite                                                                         nite    compounds (mPa.s)                                                                               Index                                     ______________________________________                                          85         53.7    21.3       300   1.15                                       90         52.8    22.2       800   1.90                                       95         51.9    23.1      2300   2.50                                      100         51.1    23.9      3200   2.80                                      105         50.3    24.7      3800   2.90                                      110         49.5    25.5      3400   3.10                                      115         48.8    26.2      3600   3.00                                      120         48.0    27.0      3000   2.50                                      ______________________________________                                    

EXAMPLE 4

The bentonite suspension and silica suspension "B" prepared as described in Example 1 above were mixed together in various proportions to give mixed suspensions each containing a different percentage by weight of silica. Each mixed suspension was prepared using the Silverson mixer at the maximum shear setting for 15 minutes. In each case there was added to the mixed suspension as mixing proceeded a quantity of an emulsion containing 1% by weight of a mixture consisting of 50 mol % of 2MBHT and 50 mol % of 2M2HT sufficient to provide 105 milliequivalents of mixed quaternary ammonium compounds per 100 g of dry bentonite.

In each case the organoclay suspension was filtered, washed, dried and milled as described in Example 1, and 1% by weight of each dry organoclay was stirred into the same polyester resin composition as was described in Example 1. The viscosity of each polyester resin after the addition of the organoclay was measured by means of a Brookfield Viscometer at a spindle speed of 0.5 rpm and the results obtained are set forth in Table IV.

                  TABLE IV                                                         ______________________________________                                         Percentage by weight of                                                                        quarternary                                                                    ammonium    Viscosity                                                                             Thixotropy                                  silica bentonite                                                                               compounds   (mPa.s)                                                                               Index                                       ______________________________________                                          0     65       35          2000   2.35                                        10     58.7     31.2        2500   2.57                                        25     48.9     26.1        2800   2.78                                        40     39.0     21.0        2000   2.50                                        75     16.3     8.7          400   1.25                                        100    0        0            400   1.02                                        ______________________________________                                    

EXAMPLE 5 Two-pack epoxy enamel paint

An aqueous suspension of bentonite was prepared by mixing raw Wyoming sodium bentonite in a blunger with sufficient water to form a suspension containing 10% by weight of dry clay. The suspension thus formed was fed to a scroll-type centrifuge which removed substantially all of the particles larger tha 50 microns. The degritted bentonite suspension was then diluted with water to a solids content of 4% by weight and passed through a No. 300 mesh British Standard sieve. The undersize fraction was subjected to a particle size separation in a nozzle discharge, disc centrifuge at a flow rate of 1 liter per minute. The fine fraction produced by the centrifuge had a solids content of 2.5% by weight.

An aqueous suspension of precipitated silica was also prepared by mixing with water by means of laboratory stirrer sufficient of a precipitated silica having an average particle diameter of 0.4 micron and a specific surface area of 200m² g⁻¹ to form a suspension containing 4.3% by weight of dry silica.

The bentonite fine fraction and the precipitated silica suspension were mixed together in proportions such that the final dry organoclay product contained 20% by weight of silica and the mixed suspension was passed once through the Manton-Gaulin homogeniser at a pressure of 4000psi (27.6 MPa), the energy dissipated in the emulsion being 968 KJ per kg of dry solids.

An aqueous suspension of 2MBHT was prepared by melting the quaternary ammonium compound/isopropyl alcohol mixture which is available in commerce and pouring the molten mixture into hot water in proportions such as to form a 1% by weight emulsion of 2MBHT in water. The emulsion was passed once through the Manton-Gaulin homogeniser at a pressure of 4000 psi (27.6 MPa), the energy dissipated in the emulsion being 2769 KJ per kg of dry solids.

Portions of the suspension of the bentonite/silica mixture were mixed with portions of the emulsion of 2MBHT emulsion at 65° C. in a paddle mixer to give the proportions of silica, bentonite and quaternary ammonium compound given in Table V, and in each case the mixture was agitated for 30 minutes and then passed once through the Manton-Gaulin Homogeniser at a pressure of 4000 psi (27.6 MPa). Each organoclay portion was then filtered, dried in an air swept oven for 16 hours at 60° C. and milled to pass through a sieve of nominal aperture 0.080 mm.

Each portion was incorporated into pack A of a two pack white epoxy paint, of which pack A is the base containing the epoxy resin and pack B is the polyamide curing agent solution.

Pack A was prepared by mixing together the following ingredients which are listed in their order of addition:

    ______________________________________                                                               Grams                                                    ______________________________________                                         75% by weight solution of epoxy resin                                                                  157.0                                                  in xylene                                                                      Solvent mixture (see below)                                                                            47.5                                                   Urea formaldehyde resin as flow                                                                        7.0                                                    control agent                                                                  Dispersing agent        3.5                                                    Titanium dioxide pigment                                                                               149.0                                                  ______________________________________                                    

The above ingredients were mixed together in a water-cooled pot using a 4 cm diameter Cowles blade at 4000 rpm. The mixing was continued until a small sample spread on a Hegman gauge gave a reading of less than 5 microns.

The speed of the Cowles blade was then reduced to 2000 rpm and there were then added:

    ______________________________________                                                           Grams                                                        ______________________________________                                         Solvent mixture (see below)                                                                        42.5                                                       Organoclay           2.5                                                       ______________________________________                                    

When all the organoclay had been added the speed of the Cowles blade was again increased to 4000 rpm and, for each batch of pack A, small samples were taken at 1 minute intervals and spread on a Hegman gauge. For each batch there was recorded the time taken to reach a state of dispersion such that the Hegman gauge gave a reading of less than 10 microns (see Table V below).

As a comparison, further batches of pack A were prepared containing organoclays prepared in a manner similar to that described above but containing no silica and the mixing time required to reach a Hegman gauge reading of less than 10 microns was recorded (see Table V below).

Each batch of pack A was mixed with a batch of pack B prepared according to the following formulation, to form a white epoxy enamel paint

    ______________________________________                                                            Grams                                                       ______________________________________                                         Polyamide liquid curing agent                                                                       56.0                                                      Xylene               35.0                                                      ______________________________________                                    

The total formulation weight of the epoxy paint was 500 grams.

The solvent mixture comprised:

    ______________________________________                                                          % by weight                                                   ______________________________________                                         Ethylene glycol monoethyl                                                                         65                                                          ethyl acetate                                                                  Methyl isobuty ketone                                                                             15                                                          Xylene             20                                                          ______________________________________                                    

The results obtained are set forth in Table V.

                                      TABLE V                                      __________________________________________________________________________                     % by weight of                                                                            Energy dissipated                                                                       Time to reach                              % by meq of quarternary                                                                             quarternary                                                                          in homogeniser                                                                          Hegman gauge                               weight of                                                                           ammonium compound                                                                              ammonium                                                                             (KJ per kg dry                                                                          reading of less                            silica                                                                              per 100 g of bentonite                                                                    bentonite                                                                           compound                                                                             solids)  than 10u (min)                             __________________________________________________________________________     20    91        57.6 22.4  1371     12                                         20   100        56.1 23.9  1396      4                                         20   114        53.8 26.2  1434      2                                         20   126        52.0 28.0  1464      4                                          0    89        72.5 27.5  1549     >30                                         0   101        69.9 30.1  1592     20                                          0   113        67.5 32.5  1632     10                                          0   119        66.3 33.7  1652     >30                                        __________________________________________________________________________

EXAMPLE 6 Gelling toluene

Aqueous suspensions of bentonite and precipitated silica were prepared using the same starting materials and preparative methods as described in Example 5.

The suspension of finely divided bentonite and the suspension of precipitated silica were mixed together in different proportions and each mixed suspension was passed once through the Manton-Gaulin homogeniser at a pressure of 27.6 MPa.

An aqueous suspension containing 2MBHT and 2M2HT in the proportions 75 mole % 2MBHT to 25 mole % 2M2HT was prepared by melting the quaternary ammonium compound/isopropyl alcohol mixtures and pouring the molten mixture into hot water to form an emulsion containing 1% by weight of the mixed quaternary ammonium compounds in water.

Portions of the emulsion of mixed quaternary ammonium compounds were circulated through the Manton-Gaulin homogeniser at a pressure of 27.6 MPa and in each case the bentonite/precipitated silica suspension was added to the feed hopper of the homogeniser in proportions such that there were present in the mixture 105 meq of quaternary ammonium compounds/100 g of dry bentonite. In each case the mixture received the equivalent of one pass through the homogeniser. The organoclay/silica composition thus formed was then filtered, washed, dried in an air-swept oven at 60° C. for 16 hours and milled to pass through a sieve of nominal aperture 0.080 mm.

Each sample of dry organoclay/silica composition was tested for its gelling properties in toluene by dispersing a 6 g sample of the composition in 340 ml of toluene in a Waring Blendor rotating at 16,500 rpm for 3 minutes. The mixture was allowed to stand for 2 hours and the viscosity the measured using a Brookfield Viscometer at a speed of 50rpm. The results obtained are set out in Table VI.

                  TABLE VI                                                         ______________________________________                                         % by weight                                                                    in organoclay/silica                                                           composition of Energy dissipated                                                            quarternary                                                                              in homogeniser                                                                            organ- Vis-                                       ben-    ammonium  (KJ Kg.sup.-1) in                                                                         clay/  cosity                                silica                                                                              tonite  compounds silica/bentonite                                                                          silica (mPas)                                ______________________________________                                          0   67.1    32.9      1089       1639   100                                    5   63.7    31.3      1055       1589   210                                   10   60.4    29.6      1023       1537   200                                   15   57.0    28.0      992        1487   290                                   20   53.7    26.3      963        1436   330                                   25   50.3    24.7      935        1386   450                                   30   46.9    23.1      908        1335   420                                   35   43.6    21.4      882        1284   520                                   ______________________________________                                    

EXAMPLE 7

Aqueous suspensions of bentonite and precipitated silica were prepared as described in Example 5 and were mixed together in proportions such that the final organoclay/silica composition contained 20% by weight of dry silica. Each mixed suspension was passed once through the Manton-Gaulin homogeniser at a pressure of 27.6 MPa.

A 1% by weight aqueous emulsion of a mixture consisting of 75 mole % 2MBHT and 25 mole % 2M2HT was prepared as described in Example 6. Portions of this emulsion were circulated through the Manton-Gaulin homogeniser at a pressure of 27.6 MPa and in each case a bentonite/precipitated silica suspension was added to the feed hopper of the homogeniser in proportions such that in each case there was present a different number of milliequivalents of quaternary ammonium compounds/100 g of dry bentonite. In each case the mixture received the equivalent of one pass through the homogeniser. The organoclay/silica compositions thus formed were then filtered, washed, dried in an air-swept oven at 60° C. for 16 hours and milled to pass through a sieve of nominal aperture 0.080 mm.

Each sample of dry organoclay/silica composition was tested for its gelling properties in toluene by the method described in Example 6 and the results obtained are set forth in Table VII below:

                                      TABLE VII                                    __________________________________________________________________________                % by weight in organoclay/                                                     silica composition of                                                                        Energy dissipated                                     meq quaternary    quaternary                                                                            in homogeniser                                        ammonium compounds                                                                               ammonium                                                                              (KJ kg.sup.-1 in                                                                        organoclay/                                                                           Viscosity                             per 100 g bentonite                                                                       bentonite                                                                             compounds                                                                             silica/bentonite                                                                        silica (mPas)                                __________________________________________________________________________      90        56.3   23.7   967      1392   800                                   100        54.4   25.6   964      1424   530                                   105        53.7   26.3   963      1436   350                                   110        53.0   27.0   962      1447   124                                   120        51.3   28.7   959      1476    40                                   __________________________________________________________________________

EXAMPLE 8

Aqueous suspensions each consisting of a mixture of water bentonite ad precipitated silica were prepared as described in Example 7. Each mixed suspension contained bentonite and silica in proportions such that the final organoclay/silica composition prepared from each contained 25% by weight of dry silica and was passed once through the Manton-Gaulin homogeniser at a pressure of 27.6 MPa.

Emulsions were prepared containing 1% by weight of mixtures in various proportions of 2MBHT and 2M2HT according to the method described in Example 6. Each batch of emulsion was circulated through the Manton-Gaulin homogeniser at a pressure of 27.6 MPa and in each case a bentonite/precipitated silica suspension was added to the feed hopper of the homogeniser in proportions such that there were present 105 meq of quaternary ammonium compounds per 100 g of dry bentonite. In each case the mixture received the equivalent of one pass through the homogeniser. The organoclay/silica compositions thus formed were then filtered, washed, dried in an air-swept oven at 60° C. for 16 hours and milled to pass through a sieve of nominal aperture 0.080 mm.

Each sample of dry organoclay/silica composition was tested for its gelling properties in toluene by the method described in Example 6 and the results obtained are set forth in Table VIII below:

                                      TABLE VIII                                   __________________________________________________________________________                % by weight in organoclay/                                          Mole % in quaternary                                                                      silica composition of                                                                        Energy dissipated                                     ammonium compound quaternary                                                                            in homogeniser                                        mixture of        ammonium                                                                              (KJ kg.sup.-1) in                                                                       organoclay                                                                           Viscosity                              2MBHT 2M2HT                                                                               bentonite                                                                             compounds                                                                             silica/bentonite                                                                        silica                                                                               (mPas)                                 __________________________________________________________________________     100    0   51.8   23.2   938      1361  470                                    75    25   50.3   24.7   935      1386  430                                    50    50   48.9   26.1   932      1409  190                                    25    75   47.5   27.5   929      1433   30                                     0    100  46.3   28.7   926      1453   30                                    __________________________________________________________________________ 

We claim:
 1. A process for preparing an organophilic composition which process comprises preparing an aqueous suspension comprising a mixture of smectite clay and finely divided silica, mixing with the aqueous suspension a quaternary ammonium compound which has at least one alkyl radical having from 10 to 24 carbon atoms and which is capable of rendering the smectite clay organophilic, either in the molten state or in the form of an emulsion in water, and subjecting the resultant mixture to high shear mixing for a time sufficient to dissipate in the mixture at least 100 kJ of energy per kg of dry solids in the mixture, said finely divided silica being used in an amount sufficient to provide at least 5% by weight of the final mixture of smectite clay, finely divided silica, and quaternary ammonium compound.
 2. A process according to claim 1, wherein the high shear mixing is effected by passing the suspension through a homogenizer of the type in which the suspension is forced in the form of a thin film edgewise through a thin, hard-surfaced gap under a pressure of at least 250 pounds per square inch (1.7 MPa) and at a high velocity.
 3. A process according to claim 1, wherein after the mixture of smectite clay and finely divided silica has been treated with the quaternary ammonium compound it is dewatered by filtration or by centrifugation, washed with water and thermally dried at a temperature not exceeding 100° C.
 4. A process as claimed in claim 1, wherein the finely divided silica has an average particle diameter in the range from 0.005 micrometers to 0.5 micrometers.
 5. A process as claimed in claim 1, wherein the finely divided silica constitutes from 10% to 50% by weight of the mixture of smectite clay, finely divided silica and quaternary ammonium compound.
 6. A process as claimed in claim 1, wherein the quaternary ammonium compound is one which can be represented by the general formula: ##STR2## wherein R₁ is a saturated or unsaturated alkyl group having from 10 to 24 carbon atoms, R₂ and R₃ which may be the same or different, are each a saturated or unsaturated alkyl group having from 1 to 24 carbon atoms or an aralkyl group having from 7 to 10 carbon atoms, R₄ is an alkyl group having from 1 to 6 carbon atoms or an aralkyl group having from 7 to 10 carbon atoms, and X is OH, Cl, Br, I, No₂, CH₃ SO₄ or CH₃.COO.
 7. A process according to claim 1, wherein the mixture of smectite clay and finely divided silica is treated with a mixture of dimethyl di(hydrogenated tallow) ammonium chloride and dimethyl benzyl hydrogenated tallow ammonium chloride.
 8. A process according to claim 7, wherein the mixture comprises from 25 mol % to 100 mol % of dimethyl benzyl hydrogenated tallow ammonium chloride and from 75 mol % to 0% of dimethyl di(hydrogenated tallow) ammonium chloride.
 9. A process as claimed in claim 1, wherein the mixture of smectite clay and finely divided silica is treated with a quantity of quaternary ammonium compound or mixture of the quaternary ammonium compounds such as to provide from 95 to 120 milliequivalents of quaternary ammonium compound(s) per 100 g of dry smectite clay. 